Williams is weighing up several options for its 2013 driver line up and will make a decision before the end of the year.

Neither Pastor Maldonado nor Bruno Senna have a contract for next season and both are under pressure after the team has struggled for results at recent races despite the car's strong underlying performance.

Maldonado brings substantial financial backing to the team and after scoring the team's first victory since 2004 earlier this season is expected to stay. Senna's position is less certain with test driver Valtteri Bottas waiting in the wings after completing a series of Friday morning practice sessions in Senna's car this year.

However, executive director Toto Wolff told ESPNF1 that the team is exploring "many options" for 2013.

"[An announcement] is going to be this year, but we don't know about the timing yet because we want to concentrate on this season and focus on our current drivers - that's important," he said. "There are many options that we are looking at at the moment and it's not an easy one."

He added: "It's a very tough decision. First of all we have been working with those guys for quite some time and of course that influences the decision a lot. It is about weighing up short-term and long-term options and sometimes the best short-term option isn't the best long-term option."

Senna and Maldonado have four races left this year to make an impression, but Wolff said the team already has a good idea of what its drivers are capable of.

"Good performances help always and it's the last race which counts. But at the moment we have seen it all and we have made up our judgement and it is about looking at all the possible options and the best for the team."

Wolff is also confident Williams can rediscover its form from earlier this year after struggling for points at recent races.

"[We're] very disappointed [with recent results], but we know the reasons why," he added. "It's just about getting everything together and I think we have seen of Korea that many other teams are having ups and downs.

"It's almost incredible that one car is performing and the other not so good, but that's what we see with tyres and with a tricky track and tricky grip levels. We haven't been so good in Korea but Singapore was fantastic in terms of the sheer speed of the car."